Answer 1

1. Here, iron powder and sulphur powder are mixed together. B is a mixture (Fe + S).
2. Here, iron powder and sulphur powder are mixed together and heated strongly on a burner. So, C is the compound iron sulphide(FeS).
3. i. Here, dilute HCl was added to C (iron sulphide)to obtain D, which is hydrogen sulphide gas.           
   FeS + 2HCl → FeCl₂ + H₂S
   ii. When dilute HCl is added to B, Fe present in the mixture reacts with the acid to form hydrogen gas.
   Fe + HCl → FeCl₂ + H₂
4. Gas D smells like rotten egg.
5. When a burning stick is held in the gas, the gas itself catches fire with blue flame and a ‘pop’ sound. In the process, the burning stick extinguishes.